Morphology and neurochemistry of two striatal neuronal subtypes expressingthe GABA(A) receptor alpha 3-subunit in the rat

The morphological characteristics, distribution and neurochemical phenotype of striatal neuronal subtypes expressing the GABA(A) receptor alpha 3-subu nit were investigated using immunocytochemical and immunofluorescent techni ques with an antibody specific for this subunit. alpha 3-immunopositive neu rons were infrequent in the rat striatum, but two morphologically different subtypes were observed: Cholinergic neurons, and a second cellular type th at may correspond to neurogliaform neurons, although it may also be a novel subtype of striatal interneuron. To identify the second cellular subtype, co-localization of the GABA(A) receptor alpha 3-subunit with markers of dif ferent classes of striatal interneurons was studied using specific antibodi es. It was found that there was a lack of co-localization between all inter neuronal markers used in this study and the alpha 3-subunit. Although the a lpha 3-subunit immunopositive neurons represent a small percentage of the t otal of striatal neuronal populations, they may play an important role in t he regulation of the microcircuitry of the striatum. (C) 2000 Elsevier Scie nce B.V. All rights reserved.